Please understand, I in no way wish to defend this film - which is awful - but I feel I must defend Mr Ustinov for the following reasons:
1) This film is NOT set in the 1980's. It's very clearly set in the 1930's, as it should be. I find it amazing that anyone could be confused on this point, since the date is given right at the beginning of the film, all the costumes and vehicles are from the 1930's, and despite the constant (and infuriating) use of 80's-sounding background music throughout - which totally ruins the movie, making it sound like a porn film - there are several party scenes that feature classic 1930's big-band tunes, which help (somewhat) to restore the period feel.
2) It's not Ustinov's fault that this is a terrible film. He's one of the only good things in it. He does his best with what he's given to work with; a terrible script, dull story, weak supporting actors (albeit famous ones), and possibly the world's worst director!
3) You can't hold it against him for accepting the job. Actors need to make a living too, you know! Few other professions would come under such attack, based on the jobs their workers choose to (or are forced to) accept. That would be like a highly recommended plumber turning down work on a building because he disliked the colour of its facade! Actors could just as easily be criticised for turning down jobs for "artistic" reasons, and then signing on the dole! They can't win! Bottom line: they are professionals working in a trade that is rife with unemployment. Even the most successful and respected ones must think very carefully before passing on a project.
4) As Michael Caine has said on many occasions, "You don't know it's going to be a terrible film when you agree to do it!"
Finally, with reference to the whole "modern day" timeframe issue, Ustinov also played Poirot in a 1980's television series, which WAS set in the "modern day". For that reason, I always avoided the TV series, and only ever watched the movies. Like you, I prefer the correct period setting. But, if - IF - "Appointment With Death" had been set in the 1980's (which it wasn't), then it could just as fairly be argued that it maintained continuity with Ustinov's currently running TV series.
To close, I should add that despite preferring films to be set in the correct time period, I allow for occasional exceptions. My all-time favourite Sherlock Holmes - Basil Rathbone - played Holmes in the correct Victorian setting, and also in a "modern-day" 1940's setting. And it worked well enough both ways. Of course, the 1940's-set films were not really authentic Holmes stories, so it was only the characters that got themselves transplanted into a WWII environment, but I still thoroughly enjoy those old Holmes classics from Universal.
As ever, it's all a matter of personal taste. Certainly NOT something for which a participating actor deserves to be attacked!
For the record, I believe Ustinov's "Death On The Nile" to be the definitive Poirot movie, closely followed by "Evil Under The Sun". These are my two favourite films featuring the Belgian sleuth, and are in my opinion perfect films. However, many people can't stand Ustinov's portrayal of Poirot, so it's very much a case of horses for courses.
Please excuse my overlong post. I seem to be suffering an attack of long-windedness! My humble apologies.
This is a part of the worst of the 80s in period films amidst some of the best films (in general) made to date.
The 80s are home to some classics, however, when it comes to authenticity - they didn't really "get it" until the late 90s through to today - why that is, I'll never know. However, I did see this movie when I was a child, when it came out on my birthday. So it holds some nostalgia for me and I'm a huge Lauren Bacall fan so there's that.
Re-watching it, though, what a campy beginning - good god.
"It's like I'm Han, you're Chewy, she's Ben Kenobi and we're in that *beep* up bar!"
They didn't get "authenticity" until today? Are you insane? It's more often miss than hit these days. The new Poirot movie being a prime example.